WORK IN PROGRESS
Here you will find insturctions for Dissolved Oxygen, Nitrate-Nitorgen, and Turbidity.These instructions give a little bit of background information on why we do these tests and then the step by step process we take to collect the data. If you have any questions contact Mark Fiorini.
Dissolved Oxygen
This test (laMotte 5860) uses the azide modification of the Winkler titration method to determine Dissolved Oxygen (DO). Results are recorded as mg/L DO and should fall between 0.0 - 15.0. Dissolved Oxygen is important for healthy aquatic life. Oxygen from the atmosphere dissolves readily into the water column. Cold water can hold more DO then warm water and algae adn rooted aquatic plants add DO to the water column durign photosynthesis. If levels fall below 5 mg/L DO, many organisms become stressed and can lead to death.
To ensure accuracy, the Water Sampling Bottle (0688-DO) should be filled directly from the body of water being sampled. There may however be times when you don ot have direct access to a site. In this case it is permissible to use the bucket to retrieve sample waters. The DO procedure up to and including Step 6 sohoudl be followed immediately.
Step 1. To avoid contamination, thoroughly rince the Water Sampling Bottle (0688-DO) 2-3 times with the water to be sampled.
Step 2. With the sample bottle pointed downstream, slowly tilt it while submerging it slightly, and allow the water to fill the bottle. It is important to avoid bubbling as the water enters, since this can artificially increase your readings. Once the bottle has filled, keep it sumerged and return it to a vertical position. Gently tap the side to remove any stray air bubbles and then cap the bottle when it is sitll under water.
Step 3. Lift the bottle out of the water, turn it upsidedown and look carefully to make sure that no air bubbles are trapped inside. Once a satisfactory sample has been collected, proceed immediately with Steps 4 through 6. Note: Be careful not to introduce air into the sample while adding the reagents in Steps 4 to 6. Physically put the dropper just above the surface of the sample bottle while adding the reagents.
Step4. Add 8 drops of Manganese Sulfate Solutionn (4167) to the sample. Be sure to hold the dropper-bottle of indicator solution vertically (not tilted) and at eye-level to dispense uniformly-sized drops.
Step 5. Add 8 drops of Alkaline Potassium Iodide Solution (7166) to the sample. Carefully cap the bottle and mix by inverting getnly 20-30 times. A precipitate (floc) will form. Allow the precitoation to settle below the sholders of the bottle. Invert the bottle again and allow the precipatate to settle totally (note the color change). The clear-yellow to brown-orange color that developes is a result of the iodine in the reagent.
Step 6. Gently add 8 drops of Sulfuric Acid (6141) to the sampling bottle. Cap the bottle and gently mix both until the reagent and the precipitate have dissolved (some suspended material may remain). Note. Step 6 "fixes" the water sample and takes about 5 minutes. Exposreu of the sample to the atmostphere will not longer effect the test results. It is not necessary to performthe rest of the procedure (the actual test) immediately. Samples fixed in the field can be carried back to a testing station , laboratory or other sheltered area for testing. Tireation (Step 9) should be completed no longer than 8 hours after fixing.
Step 7. Rinse the Tiration Tube (0299) with distilled water, the pour the fixed DO sample into the tube filling so that the bottom of the meniscus is level with the whilte (20ml) line.
Step 8. Fill the syringe-like Titrator (0377) to the "0" mark with Sodium Thiosulfate Solution (4169) making sure no air bubbles are in the Titrator. The next step is called titration.
Step 9. Titrate the sample using the following guidelines: Insert the Titrator into the hole in the cap of the Titrator Tube. Add 2 drops of Sodium Thiosulfate Solution to the Titration Tube and gently swirl to mix. Keep adding Sodium Thiosulfate Solution 2 drops at a time and swirling until the yellow-brown color of the solution begins to fade (iodine reduciton in occuring). Stop when the solution is a pale yellow (straw-colored). Remove the Titrator and store in its protective sleve in the DO kit (do not remove the remaining Sodium Thiosulfate Solution!).
Step 10. Add 8 drops of Starch Solution (4170) to the Titration Tube. Swirl the tube to mix. The solution should turn from light yellow to dark blue (this indecates that the iodine has been neutralized).
Step 11. Remove the Titrator from the kit, insert into the Tirator Tube (with the scale facing you) and inject 1 drop of Sodium Thiosulfate Solution and swirl. Continue this process unitl the solution turns from blue to clear.
Step 12. Using the scale on the side of the Titrator, record the total number of units of Sodium Thiosulfate used in titration (this amount equals the mgO2.L in the water). Note both the whole and the 0.2 unit graduations on the side of the Titrator. Read the results from the widest part of the titrator tip. (see page 10 of LaMotte directions for diagram of titrator). Record results.
Step 13. Empty the Titration Tube and rinse it with distilled water Return to Step 7 and perform a second titration with the existing fixed sample.
Step 14. Record the two acceptable readings on teh data sheet, then record teh average of those tests. This is your DO reading for the period. Note: At least two titrations are required for accurate DO measurements. If the amount of DO in the second titration varies from the DO from the first titration by greater than 0.6 mg/L, you must do a third titration. Record the average of the two lowest results on the Data Sheet.
Step 15. Discard waste reagents by diluting and dumping 50 yards from the stream in a vegetated area. Rincse equipmetn with distilled water adn replace in the kit. DO NOT remove the blunger or adapter tip (green and pink) from teh titrator for rinsing.
Nitrate-Nitrogen
Nitrogen is required for all organisms for building proteins. Nitrate is essential for plant growth and is used in agriculture (including Sludge application) and lawn fertilizer. Nitarates from these sources enter the water system when excessive nitrate not taken up by the crops, runs off into nearby streams. Other sources of Nitrate include failing on-lot septic systems, sewage treatment plants, runoff from animal manure storage areas, industrial and packing house wastes, drainage from livestock areas and industrial discharges that contain corrosion inhibitors
An increased concentration in Nitrates in a water system can result in an "algal bloom" or eutrophic conditions (when sunlight cannot penetrate the water, causing dangerously low oxygen conditions, otherwise known as "dead zones"), which causes an increase in plant growth in a water system and a "choking out" of fish and other macroinvertebrates. When the Nitrate is used up by the plants and algae, this plant material dies and the decay process robs Dissolved Oxygen from the water, often causing fish kills. The <st1:statew:stonstylefont-family: tahoma;><st1:placew:ston>Pennsylvania standard for Nitrate-Nitrogen is a maximum of 10.0ppm or mg/L (as of 12-23-07). Scientists agree that Nitrates less then 1 mg/L have no negative impact on the stream and the organisms that rely on it. As nitrates increase above 1mg/L, negative impacts can incur.
Ortho-Phosphate
Phosphorous usually occurs in nature as Phosphate and is crucial for the formation of DNA and proteins. Phosphate(PO4) is found in two forms in aquatic systems and both can either be dissolved in the water or suspended (attached to particles in water). Organic Phosphate is bound to plant or animal tissue. Inorganic Phosphate (Ortho-Phosphate) is the form most readily available to plants, and thus the most useful indicator of immediate problems with excessive plant and algal growth. Ortho-Phosphate is also the easiest form to measure.
In many natural waters, Phosphate concentrations are normally low (less then 0.01 mg/L). When levels become greater then 0.1 mg/L, this often indicates pollution. Phosphate is usually the limiting nutrient for plant growth, meaning it is in short supply relative to Nitrogen. To find out where this comes from, refer back to Nitrogen. The results from plant decay are also the same as Nitrogen.
